In a new study, astronomers have compiled a list of nearby star systems where inquisitive inhabitants of orbiting planets might well have discovered life on Earth.
Scientists identified 1,715 star systems in our cosmic vicinity where alien observers might have discovered Earth in the past 5,000 years by observing its “transit” around the sun.
Among those in a suitable position to observe Earth’s transit, 46 star systems are close enough for their planets to intercept a clear signal of humanity’s existence — radio and television transmissions that began about 100 years ago.
Researchers estimate that 29 potentially habitable planets stand a good chance of witnessing Earth’s transit and overhearing huмคห radio and television transmissions, allowing any observers to infer a possible level of intelligence. Whether these transmissions will cause an advanced civilization to make contact is a difficult question.
To find out which nearby stellar systems might observe Earth’s transit, Kaltenegger and Dr. Jackie Faherty, an astrophysicist at the American Museum of Natural History, turned to the European Space Agency’s Gaia catalog of star positions and movements. From it, they identified 2,034 star systems within 100 parsecs (326 light years) that could spot Earth transiting any т¡мe between 5,000 years ago and 5,000 years in the future.
One of the stars known as Ross 128, a red dwarf in the constellation Virgo, is about 11 light-years away — close enough to receive radio transmissions from Earth — and has a planet nearly twice the size of Earth. Any intelligent life on this planet could have observed Earth’s transit for more than 2,000 years, but lost its vantage point 900 years ago. If one of the two known planets orbiting the star Teegarden, 12.5 light-years away, has intelligent life, it could observe Earth transits in 29 years.
45 light-years away is another star called Trappist 1, which is also close enough to eavesdrop on huмคห transmissions. This star has at least seven planets, four of which are in the temperate, habitable zone, but they won’t be able to observe Earth transits for another 1,642 years, scientists wrote in the journal Nature.
The findings come as the U.S. government prepares to publish a long-awaited report on unidentified flying objects (UFOs). It is expected that the report of the Pentagon’s Task Force on Unidentified Aerial Phenomena, established to clarify the nature and origin of unknown flying objects will not be able to provide evidence that they are alien vehicles, but at the same т¡мe cannot rule out the possibility.
Professor Beth Biller of the Institute of Astronomy at the University of Edinburgh, who was not involved in the Nature study, said the work could change the way scientists approach the search for extraterrestrial life. “I was struck by how few stars within 100 parsecs could observe transiting Earth,” she said.
“The transit method requires a very precise alignment between the transiting planet, its star and the Sun to detect a given planet, so this result is not surprising. Now I wonder what proportion of the stars in Gaia’s catalog of nearby stars have the right vantage point to detect Earth using other exoplanet detection methods, such as the radial velocity method or direct imaging!”